The present invention relates to a wastewater or sludge treatment fixed film cross-flow distribution media sheet having a unitarily formed end baffle and assemblies thereof that may include other components. Various embodiments are presented. They are used in well-known wastewater or sludge treatment processes, such as Integrated Fixed-film Activated Sludge (IFAS) processes and Submerged Fixed Film (SFF) processes.
More particularly, the sheet of the present invention is corrugated with corrugations angled at an angle of about 10° to about 80° with respect to the top and the bottom of the sheet where the corrugations of adjacent sheets with or without an optional substantially planar sheet between them are angled in opposite directions and formed into one or more assemblies within a treatment basin. The oppositely angled corrugations on adjacent corrugated sheets provide for translation of the wastewater or sludge and any entrained air from a single point source to two or more point sources and subsequent redistribution above in the assembly. The corrugated sheet with the unitarily formed baffle and assemblies thereof provide excellent available surface area for biological attachment used in wastewater and sludge treatment. The bacteria and other microorganisms, referred to as “biomass” are beneficial in the treatment of wastewater or sludge and form a “biofilm” on the corrugated sheets and other components of the assemblies with enhanced ability to control the contact of wastewater or sludge with the biofilm and performance of the biofilm and the enhance control of the supported biomass, by which the wastewater or sludge and air being sparged through an assembly or assemblies of the sheets are distributed effectively throughout the assembly to enhance the treatment of the wastewater or sludge.
Forming the sheets with the unitary baffle into the formed distribution media sheet reduces the necessary labor and associated cost of a secondary manufacturing process, reduces quality issues with gluing a separate section of material to the end of the media pack, and reduces damage to the sheets and assemblies during shipping and installation. In addition, problems, such as increased cost, damage and inefficiencies associated with additional materials used in making assemblies using the prior art sheets, are overcome with the present invention. In view of the unitary baffle formed on the sheets of the present invention, a secondary process needed to make separately attached baffles, such as extruded parts, shearing or sizing of baffle material involved as intermediate manufacturing steps using additional equipment, preparation of the existing media pack for inclusion of baffle (i.e., slicing a slot for fitting the extrusion), and ultimately assembly of the multiple components needed to install the baffle on the media assembly can be avoided. Significant damage to the media baffle used in the prior art assemblies occurs during shipping, as the packs are slid across the top of other packs during unpacking and assembly of the media towers causing the baffle and/or extrusion to become free at one end. Typical construction specifications do not allow for site repair of damaged media and the material must be returned to the factory or disposed of at the construction site.
The present invention solves these problems of the prior art cross-flow distribution media sheets and assemblies made from them. The presence of a unitary baffle as an integral part of the sheet of the present invention eliminates the need for separate baffling elements and seals the either or both sides of the assembly of sheets that is or are exposed to denser wastewater or sludge from a downcomer region in the basin outside of the assembly from intrusion into the assembly and escape of air from sparging under the assembly, enabling the entire assembly plan view to contain releasing air bubbles and therefore generate upward flow and complete biofilm control on the media surface.
In one embodiment, the unitary baffle is formed along at least a top portion of an exposed side of the sheet that is exposed to the denser wastewater or sludge, and is sufficient, when joined with either a like baffle on a like sheet or an optional substantially planar sheet positioned adjacent the front or rear surface, to substantially block air from exiting the exposed side of the sheet or the denser wastewater or sludge being treated from entering the exposed side of the sheet.
In another embodiment, the unitary baffle is formed as a substantially flat generally vertical extension extending in a direction generally perpendicular to a plane corresponding to the peaks of the corrugations or to the valleys of the corrugations and extending at least the thickness of the sheet. A further embodiment just has the front and rear sheets with the unitary baffle in the form of a substantially flat generally vertical extension that extends at least slightly more than half of the thickness of an assembly containing them by which the substantially flat generally vertical extensions overlap to form a baffle for the assembly.
Further by way of background, and to help understand the environment of the invention, structured sheet media, such as made from assemblies or packs of corrugated sheets, have been used in trickling filters. When so used, studies have been performed that concluded that vertical flow media, where the corrugations are generally vertical, rather than angled from the vertical, is not optimal for trickling filter use, because localized areas of the media surface become un-wetted through poor redistribution and the effective surface area for biomass growth is reduced. The accepted solution described in literature and industry publications is the use of cross-flow media where the corrugations of the corrugated media sheets are angled from the vertical, preferably on the order of about 30° to about 60° to allow for continual redistribution of the wastewater or sludge being treated and the air flowing through the media to treat the wastewater or sludge. Vertical flow media is installed beneath which has no cross corrugations where solids can accumulate. During this redistribution, air flowing into the tricking filter through natural or forced ventilation contacts the wastewater into which the oxygen from the air dissolves and is carried into the biomass where it is consumed by the bacterial populations for oxidation of both carbon (Biochemical Oxygen Demand or BOD) and nitrogen species (ammonia nitrogen or NH3—N). Necessary biofilm control is accomplished through flushing of the media surface or termed Spülkraft flushing intensity (in mm/pass of distributor arm). Although wastewater bypass of the biomass on the media increases causing reduced effluent quality during the flushing event, the excess flushing intensity erodes thicker older biomass allowing freer air flow (reduced head loss) and new growth to form for improved overall performance. The older biomass is typically in the form of higher microorganisms and macro fauna (e.g., snails) which depends upon the periodicity of flushing and the wastewater characteristics that must be flushed to maintain a healthy bacterial population.
Air lift pumping is a common method for moving wastewater in municipal and industrial treatment plants. Aerators placed beneath structured sheet media towers (assemblies of sheets stacked above each other) have been used in the past to provide the required oxygen demand and mixing for SFF and IFAS processes.
A commonality exists between the operating requirements of a trickling filter and its SFF technology. The basis for operation of a trickling filter applies to submerged structured sheet media used in SFF technology although the method for achieving performance may differ due to the differences in configuration. Submerged structured sheet media operates on the same principal of providing a surface area for growth; however, the submerged nature of the application is sufficiently different to warrant another approach to normal operation and biofilm control. Because the media is submerged, it supports different biomass populations on its surface and is not necessarily susceptible to the same nuisance macro fauna, but to other populations that must be addressed. Additionally, because dissolved oxygen is required for the BOD and NH3—N removal, air sparging is the most common and cost efficient method of transferring the required oxygen. Utilizing the air sparging to provide a single solution to these two issues of aeration and scouring has been difficult and has not been effectively achieved in the past. The major issues have been: (1) media plugging, (2) incomplete or marginal distribution of the sparged air, (3) recombination of the sparged air to form large bubbles, and (4) “necking” of the air plume within the media tower to form a narrowing plume beginning from emergence from the diffuser and continuing up to breaking the surface of the water.
Cross flow media is made up of a series of corrugated sheets of alternating direction typically at approximately 30° to approximately 60° opposing angles, measured from the bottom of the media. Because of the configuration of the sheet, communication of water and air flow can occur between these sheets and because the media is cross-stacked when installed for structural integrity, “necking” within the media tower occurs in both perpendicular plan view directions. The introduction of sparged air to the bottom of the media can also cause localized up flow where air is rising and down flow interstitial to the diffuser locations where the water returns to the bottom. An aeration pattern is typically visible at the water surface which is indicative of the aeration diffuser positions beneath the towers. The mini-currents developed and additional larger areas at the outside edges of the media tower limit the air bubble contact of the media surface (or attached biofilm surface) in the downward flowing areas because air bubbles are not as prevalent, nor are they rising. The direct impingement of the air bubbles limits the attached growth depth or thickness through biomass erosion. In areas where the flow is downward, some biomass control through water velocity scouring is realized. Minimally effective biofilm control exists in areas that are at the outer edge of the tower or under a “transition zone” of limited water velocity, or air impingement occurs under generally localized steady state conditions. Excess biomass begins to overwhelm and plug the media and the sparged air bypasses (goes around) the plug. Once this process begins, it is difficult to clear the dense anaerobic solids mass (now devoid of oxygen) within the media. Localized areas of larger bubbles than the bubbles delivered by the installed air sparger diffusers indicate that adequate aeration is present even though these areas are a result of other areas that are plugged.
Vertical-flow media preceded cross-flow corrugated media and was used in trickling filters and consisted of a series of vertically corrugated sheets. The current application for vertical flow media is for use in retrofitting Activated Bio-Filter (ABF) technology that used redwood slats to provide splash aeration to an activated sludge process and for very high solids loaded industrial applications. The ABF technology was an improvement over systems relying on poorly designed blowers which required maintenance and energy in excess of centrifugal pumps. High solids introduced to the top of a trickling filter flush more easily from a completely vertical flow media tower as crossing points of the cross corrugated media tend to accumulate rags (cellulosic and other material that agglomerates together to form what appears to be a rag).
The concept of a mixed media system incorporating combined vertical-flow and cross-flow media integrates the individual benefits of ease of flushing of the vertical-flow media with the superior distribution of cross-flow media in the tricking filter. While the use of mixed media in trickling filters is becoming more common, submerged applications of combined cross-flow and vertical-flow towers had not been done prior to the introduction of Brentwood Industries, Inc.'s AccuFAS® product line. The vertical-flow media enables a much higher surface density to be realized over cross-flow media alone for the same corrugation or flute size or opening. The reason for this is strictly due to the doubling of the number of alternating offset sheets required for the same pack width in the layup direction (i.e., more material). Improved distribution of sparged air beneath a vertical-flow structured sheet media tower is necessary to enable the process value of high surface area density media in terms of increased biofilm inventory, reduced biofilm thickness (reduced influence of diffusion limitations), and biofilm control. This is where cross-flow “distribution” media provides a great benefit by enabling the use of the high surface area vertical-flow media.
Air lift pumping is a common method for transfer of wastewater and high solids content mixed liquor suspended solids. Typical air lift pumping is accomplished by sparging air into a vertical pipe, either at the lower end of the pipe or some intermediate position along the pipe. When the air combines with the fluid, the density of the wastewater in the pipe is reduced to a level below that of the surrounding wastewater. The outside wastewater “pushes down” on the wastewater near bottom of the pipe and hydrostatics takes over, as the height of fluid in the pipe must be greater than the surrounding wastewater proportional to the amount of wastewater displaced. The pipe walls act to provide a barrier to the air/wastewater inside the pipe and the wastewater outside the pipe to provide a density difference.
Wastewater being air lift pumped in a structured sheet media tower must be returned to the bottom of the tower via a “downcomer” where no media is installed between sequentially installed towers in a basin (or the tank end wall for the first and last towers) for circulation. The returning water must recombine with newly sparged air that leaves the diffusers installed beneath the towers. The recombination of the distinct two phases of water and air is critical because narrowing of the air flow, called “necking,” from lateral flow under the tower limits complete lateral distribution of flow within the entire plan view area of the tower, and ultimately limits impingement scouring and full tower up flow and thereby limits mixing of the wastewater or sludge with the air.
Standard air delivery technology using typical diffusers for wastewater applications provide point (disk) or line (tubular) source air distribution. The returning water flow must flow to the bottom center of the media tower for recirculation without moving laterally or “pinching” the air flow in the cross-current water flow. The current diffuser technology provides point or line source distribution which can be seen on the surface of the basin above the towers. It must be noted at this point that vertical-flow media is self baffling as it is a vertical tube. The distribution media and associated baffle at the side or sides exposed to the denser wastewater must serve as a boundary to turn or direct the flow under the tower, rather than allow bypass between the series of cross corrugated and any planar interstitial sheets between the corrugated sheets where they terminate to form the sides of the media pack exposed to the denser wastewater. The redirection of flow around the bottom layer of distribution media also serves to ensure that the floor is scoured of solids.
The distribution media usually includes an alternating cross corrugated sheet followed by a partial height (typically 50% of pack height) interstitial planar sheet to separate the wastewater, and air and wastewater paths to opposing offset geometric locations. In distribution media, the bottom half of the media pack does not allow for lateral communication, as the partial planar sheet eliminates communication between sheets. Currently, full height external end baffles as separate components to the sheets and assembly packs have been installed at the exposed end of the media packs at the cross corrugated sheet termination point to prevent the horizontal flow of water into the media and/or loss of air outside of the media. This promotes the separation of and the difference in density of the downcomer flow and upward flow of water being pumped. Typically, the baffles are glued directly to the end of the media pack and in some cases and edge or corner “J” extrusions are used to protect the edge and provide more positive attachment.
Vertical-flow media packs do not require end baffles as the vertical tube is substantially closed to lateral flow. Small gaps in the assembly of vertical-flow sheets at the offset which are necessary for tolerance and alternating assembly of the offset sheets do not interfere with the general operation of the vertical-flow media as a tube providing density separation. Small gaps at the horizontal interface in the assembly of media packs stacked to form the tower also do not negatively affect the capability of the vertical-flow media tower to support air lift pumping at a level sufficient for air scouring of the vertical and offset surfaces. Unless a substantial difference in air flow distribution exists within the vertical-flow media tower, the entire tower provides upward flow through air lift pumping. The distribution media eliminates, or if a diffuser is damaged, minimizes the potential for this difference in air flow distribution.
The fixed film cross-flow distribution media sheet having a unitarily formed exposed side baffle according to the present invention and assemblies made using them overcome the disadvantages of the current systems and apparatus and provide efficient and effective treatment of wastewater or sludge, while reducing the cost of labor involved with assembling separate baffles at the exposed ends of the assemblies of packs and towers, as well as significantly reduce or eliminate the additional handling for the separate baffle installation that is a source of downtime, and fairly often, damage to the baffle or the assembly of sheets.